Scottish National Dictionary (1700–)

1. In pl.: the holes of a musical wind-instrument, as in a flute or the chanter of a bagpipe (Sc. 1721 Ramsay Poems (S.T.S.) I. Gl.); the pipes themselves. Comb. back-lill, the thumb-hole in the back of the Lowland or Northumbrian small-pipe chanter, the upper G note.
Rxb. c.1734 Trans. Hawick Arch. Soc. (1913) 56: A blyther lad ne'er buir a drone, Nor touched a lill.Sc. 1788 in R. GallowayPoems 154: Go on, then, Galloway, go on, To touch the lill and sound the drone.Sc. 1824 ScottRedgauntlet Letter xi.: He could play weel on the pipes; and he had the finest finger for the back-lill between Berwick and Carlisle.Fif. 1870 R. ChambersPop. Rhymes 105: Jock made a pair o' lulls to his sel' … played upon his lulls sae bonnie bonnie, that the hares a' danced round.

2. Fig. A stalk of oat-straw.
Lnk. 1826 Caled. Mercury (6 July): Short in the hose, and lang in the lill — Man and beast may eat their fill.